Encryption used by most email software — from Outlook and Windows Mail to Thunderbird and Apple Mail — can be intercepted by hackers who can read at least parts of the written text, a German-led research team announced on Monday.

Academics from Münster University of Applied Sciences, along with their peers at Ruhr University Bochum and KU Leuven in Belgium, said they were able to break two types of encryption that until now were so secure that even intelligence agencies couldn’t penetrate them.

Several tests, which were overseen by reporters from German daily Süddeutsche Zeitung (SZ) as well as public broadcasters NDR and WDR, showed severe weaknesses in the S/MIME and OpenPGP standards.